This is a blind systematic follow-up study by personal interview of 153 inpatients diagnosed as having schizoaffective and related psychoses (i.e. schizophreniform illness, nonprocess schizophrenia and acute schizophrenia) and their first degree family members. This group of 153 patients constitutes a sample of a total of 305 patients with the same diagnosis whose records will be studied first. The purpose of this study is to resolve the disagreements concerning the nature of this group of psychoses by testing the hypotheses that schizoaffective and related psychoses are: (a) A variant of schizophrenia, (b) A variant of affective disorder (c) A third psychosis, defined by criteria and distinct from both schizophrenia and affective disorder, (d) A group of psychoses which at first cannot be diagnosed but eventually are recognizable as either schizophrenia or affective disorder. The proposed diagnostic criteria for a third psychosis are based on the following: (a) The psychotic patients should have a sufficient number of severe affective symptoms to make the diagnosis of schizophrenia unlikely, at least six out of a total of 17 affective symptoms. (b) The psychotic patient should have a sufficient number of qualitatively different severe thought and behavior disorders to make the diagnosis of affective disorder unlikely, at least two out of a total of five.